1. Field of Invention
This invention relates to a carrier base material adapted to be combined with a therapeutically active medicament and formed into a solid shaped dosage unit having a long-lasting and regular incremental release of the medicament upon administration. Specifically, this invention relates to a carrier base material, consisting essentially or predominantly of hydroxy-propylmethylcellulose, whose structure has been modified for use in prolonged release therapeutic compositions.
2. Description of the Prior Art
Hydroxypropylmethylcellulose has been used in the preparation of buccal or sublingual products for transmucosally acting medicaments, as described in British Pat. Nos. 1,171,691 and 1,279,214 and U.S. Pat. No. 3,870,790. Hydroxypropylmethylcellulose has been considered to be lacking in the most desirable properties for making compressed long-lasting troches and, as a result, dry skim milk powder combined with guar gum has been substituted (U.S. Pat. No. 3,590,117). Carboxypolymethylene and sodium caseinate have also been used for the same purpose (U.S. Pat. No. 3,594,467).
While it is known that buccal or sublingual lozenges and tablets intended to be swallowed can be made with various active agents and carriers, where steady prolonged medication is required and a regular rate of release is needed with good absorption of medicament, no fully satisfactory carrier has heretofore been produced. Lowey et al. (U.S. Pat. No. 3,870,790) disclosed a process for preparing a long-acting composition consisting of a therapeutic agent and a carrier, wherein the carrier consisting essentially of hydroxypropylmethylcellulose or hydroxypropylmethylcellulose admixed with ethylcellulose, is subjected to controlled humidity for a time sufficient to establish a moisture content of from about 5 to 25% and then mixed with the therapeutic agent. The present invention is directed towards further improvements in carrier bases prepared from hydroxypropylmethylcellulose.